Bone anchored bone conduction hearing aids are essential for the rehabilitation of patients suffering from some specific type of hearing loss for which traditional hearing aids are insufficient. This type of device consists of an external hearing aid with a vibrating transducer which is connected via a coupling to a skin penetrating abutment mounted on an implant fixture anchored in the skull bone. It is important that the coupling is sufficiently firm, to avoid poor transmission of the vibrations, but it is also important that the coupling is not too firm, since it is also important that the hearing aid falls off in case of a sudden impact, to avoid that the skull bone anchoring is damaged. In a coupling like this there are always coupling forces pressing components in the connection against the abutment. The coupling forces can be generated by a separate spring, a flexible material or by a magnet. The patient takes on and off the hearing aid daily, so wear and tear durability of the coupling is also important.